Beacon system



D. 24, HIMMEL v2,412,986

BEACON SYSTEM Fild March 1o, 1945 IN V EN TOR. LEO/V H/MMEL Patented Dec. 24, 1946 'f BEACON SYSTEM Leon Himmel, Bronx, N. Y., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application March 10, 1945, Serial N o. 582,051

(Cl. Z50-11) 9 Claims.

This invention relates to directive radio systems and more particularly to such systems for use in guiding beacons, localizing, radio ranging and the like.

The invention is in the nature of an improvement on the type of system shown in U. S. Patent No. 2,293,694 to A. Alford, granted August 25, 1942, although in certain of its aspects the invention is capable of use in other types of directive radio systems.

A principal object of the invention is to provide an improved course localizing arrangement by means of radiation patterns and wherein the possibility of course identification is materially increased.

Another object is to provide a course defining or localizing system using a radiation pattern of the snif-table lobe type, wherein the individual lobes are identified by respective modulation frequencies and the chances of relative error in following the course are reduced by applying the identfying modulations to a common modulator.

Another object is :t provide a course dening or localizing system employing an vantenna array comprising a so-called carrier antenna and a plurality of side-band antennae spaced therefrom, and wherein the side-band antennae are keyed at a predetermined rate so that the respective side-band radiation patterns `are modulated at identifying audio frequencies. In this way, the possibility of error resulting from a dissimilarity in separate modulation tubes is avoided.

A feature of the invention relates to a directive radio system employing a radiation pattern of the shiftable lobe type for defining an oncourse region, wherein the shifting of the lobe is controlled by a switching device which also acts to apply lobe identifying modulations to a common modulator .to control the off-course eld pattern.

Further objects and advantages will be apparent from a consideration `of the following detailed descriptions and the appended claims, and from the appended drawing illustrating one preferred form of the invention.

Fig. 1 shows in schematic form a course localizing or guiding system embodying principles of the invention.

Fig. 2 is a, schematic representation of a typical receiver and indicator arrangement that may be used with the system of Fig. 1.

Inasmuch as the invention relates to systems of Athe type shown in U. S. `Patent No. 2,293,694, only to the bridge in phase.

those parts of a complete radio guiding or locating system are shown as are necessary to an understandingof the inventive concept. It will be understood therefore, that the disclosure of said Patent No. 2,293,694 shall form part of the present disclosure.

In Fig. 1 of the drawing, there are shown three directive antennae, I, 2 and 3, which may be in the form of vertical dipoles, and each -of which may be tuned by the associated adjustable transmission line sections 4, 5 and 6. Antenna I, which may be termed the carrier antenna is located between the antennae 2 and 3 which may be termed side-band antennae. Antenna I is fed with radiant energy from the high frequency carrier source 'I over one diagonal of a hybrid bridge arrangement 8. As shown, source 1 is connected to one end of said diagonal through a suitable carrier power amplifier 9, and the other end of said diagonal is connected to the source 1.through another power amplifier I 0 which is arranged -to be modulated at audio frequency as described hereinbelow.

The energy from the two amplifiers is applied Energy from source 'I is also supplied to the side-band antennae 2 and 3 over respective transmission lines II, I2, which are fed from the opposite diagonal of .the bridger through a switching device or link relay I3, arranged to be operated at any desired keying rate so as alternately to reverse the relative phase of the energy feeding antennae 2 and 3. The carrier is substantially balanced out at the lower terminal of bridge 8 so that only the side-band energy reaches antennae 2 and 3. The antennae 2 and 3 are fed at 180 degrees phase opposition by reason of the transposition I4.

The eiect of the carrierantenna and the al- Iternating phase reversal of the side-band antennae coupling is to provide a field pattern in the general shape of a directed beam which osclllates to either side of a common symmetry line which defines the course or directivity path to be marked.

In accordance with the present invention, in addition to the alternating switching of the lobes of the field pattern, each lobe is identified by a corresponding low or audio frequency signal which may be in ,the form of an audio frequency modulation. For this purpose, the switching relay I3, in addition to the normal switching contacts (not shown) for controlling the energy supplied lines I I and I 2, is also provided with a moving contact arm I5 and a cooperating pair of fixed contacts I 6, I1. 'Contacts I6 and I'I are 3. supplied with respective low or audio frequency signals, e. g., 90 and 150 C. P. S., through respective filters I8, i9, which in turn are supplied with 90 and 150 C. P. S. signals from a common low frequency oscillation source 20. Source may be of any well-known kind which is capable of generating simultaneously with the requisite stability, the 90 and 150 C. P. S. signals. If desired, Ithe source 20 may .take the form of twoA oscillators of 120 and 30 C. P. S. which are mixed in a suitable common mixer tube or device to produce the upper and lower beat frequencies of 150 and 90 C. P. S. Whichever method is used to produce the audio frequency signals, these signals should be so adjusted that they are of substantially the same amplitude when applied to contacts I6 and l1.

Contact arm l5 is connected to amplifier l0 so as to subject the carrier passing through the amplier to an amplitude modulation in any wellknown manner. The net result is that the radiation pattern as seen from one side will be a modulated high frequency envelope having superimposed on it a square wave of frequency controlled bythe relay f3. Thus, on one side of the course, a square wave modulated with one frequency, e. g., 90 C. S., will exist. On the other side of the course a square wave modulated with the other frequency, e. g., 150 C. P. S., will exist.

Any Well-known form of radio receiver may be used aboard the moving craft which is to be guided. It may consistof a radio receiver 2l whereby the two audio frequency modulations of 90 and 150 C. P. S. may be detected and amplified and applied to the control elements of the wellknown crossed pointer indicator 22. In accordance with standard practise, the output of the receiver is shunted by a condenser 23, e. g., 1000 mfd., so as to provide a steady indication b-y the indicator needle. The overall effect, therefore, will be the same as if the two audio frequencies were on simultaneously. It will be understood, of course, that the invention is not limited to an equal timed switching of the antennae 2 and 3.

For example, the switching may be effected in accordance with conventional AN practise so that when the craft is on course, a Vcontinuous'signal is produced in the aural signal device 24.

When the craft is to one side of the course the signal will be keyed at the characteristic A rate, while at the other ide of the craft the signal will be keyed at the characteristic N rate. Likewise, if desired, the audio frequencyr modulators may be applied to amplifier 9 instead of to amplifier id.

One of the advantages of the system as above described is that the timing or operation of the relay i3 does not affect the marker course. Thus if the relay stays on one side more than on the other, while it will cause the proportion of sidebands present at each side of the course to change, it will not affect the course at all. This will be apparent since the energy from side-band radiators 2 and 3 is null along the course line.' The eect of unequal timing will merely cause ,the sensitivity upon departure from course to be greater on one side than on the other. Furthermore, since only one power amplifier, namely amplifier lil, is modulated, the operating conditionshare not changed for each modulating frequency. If the two frequencies were applied to separate modulators it would be extremely' difficult to insure that at all times the two modulators main-rV tain the same electrical characteristics. By feed- Gil 4 ing both the audio frequency signals into the common amplifier modulator this difficulty is avoided.

What is claimed is:

l. A directive radiant pattern system comprising means to develop in space a field pattern having off-course side-band lobes and an oncourse carrier lobe dening a desired course, means to phase reverse said side-band lobes at predetermined rates, and means to modulate the energy in said lobes at respective but different low frequencies and in timed relation with the phase reversal.

2. A system according' to claim l in which the means to modulate said energy comprises a single modulator upon which both the low frequency modulating voltages are impressed.

3. A directive radiant pattern system comprising a set of three antennae, a high frequency carrier source, means to apply carrier energy from said source to one antenna, means to excite the other antennae in phase opposition under control of the carrier energy, means to control the latter excitation alternately, and means to modulate at a plurality of distinctive low frequencies the excitation of said other antennae.

4. A directive radiant pattern system comprising a first radiator, a pair of radiators spaced from the first radiator on opposite sides thereof, said pair of radiators being arranged for excitation in phase opposition, a common source of high frequency energy for all said radiators, a four-armed bridge network, means connecting said pair of radiators in phase opposition to an apex of said network, means connecting the opposite apex of said network to the first radiator, means connecting said source cophasally to the other two apexes of said network, means to modulate at distinctive low frequencies the energy supplied to one of said other apexes, and means for rendering the excitation of said pair of radiators alternately effective in identifying a course line defined by the overlapping eld patterns from all said radiators.

5. A directive radiant, pattern system of the type having a central radiant acting member, other radiant acting members spaced from the central member to pro-duce overlapping fields having distinctive signal characteristics in each of two directions to define a path in space, a carrier source, a hybrid bridge network having two diagonals, means connecting the end of one diagonal to the said central member, connecting means between the other end of said one diagonal and said other members to excite said other members in phase opposition, a switching device in said connecting means for rendering said other members alternately effective in identifying a course line defined by the overlapping field patterns from all said members, a pair of amplifiers connected to said source, one amplifier being connected to one end of the second diagonal of the bridge, the other lamplifier being connected to the opposite end of said second diagonal, and means to modulate one of said amplifiers alternately by distinctive low frequency signals. v

6. A directive radiant pattern system of the type .having a central radiator and side-band radiators which are excited from a common carrier 'source through a hybrid bridge network to produce overlapping elds having distinctive signal characteristics `in each of two directions dening a path in space, characterizedby the novel `features that the opposite ends of onediagonal of said bridge are connected through respective 5 power amplifiers to the carrier source, and means are provided for modulating one of said ampliers by a plurality of distinctive low frequency signals in alternating succession.

7. A directive radiant pattern system according to claim 6 in which the central radiator is connected to one end of the other diagonal of the bridge and the other end of said other diagonal is connected through a switching relay to said side-band radiators.

8. In a system of the character described, an antenna array comprising a carrier antenna, a pair of side-band antennae spaced from the car* rier antenna, a source of carrier energy, a pluralty of paths connected to said Isource each including a separate carrier amplifier, a hybrid bridge network connecting said amplifiers to said antenna array, a switching device also connected to said network for rendering the side-band antennae alternately effective at a predetermined succession, means to develop two low frequency signals of substantially the same amplitude, and means for applying said low frequency signals to one of said ampliers alternately under control of said switching means to modulate the output of said amplier.

9. A system as claimed in claim 8 in which said switching means is keyed in accordance with predetermined distinctive code signals which produce a continuous signal along the course to be marked but which produce individual code `signals on opposite sides of the course, and said 10W frequency signals identify the respective sides of the course.

LEON HIMMEL. 

